when there is 3.0 x 10^20 molecules in a closed container, the pressure is 1.2 atm. Using a pumper 1.5 x 10^20 more molecules are added to the container. what is the new pressure?

Looking at the universal gas law, PV = nRT.

So, with T, R, and V constant, P is proportional to n; therefore, wouldn't P1/P2 = n1/n2 ?